Aura Help Center

Spectral

The Spectral meter displays the frequency content of an audio signal

In the default preset, low frequencies are on the left and high frequencies are on the right, and low magnitudes are toward the bottom and the high magnitudes are toward the top. The rulers, available on all sides, label important positions on the grid.

Crosshairs

Click and drag in the meter to display location details.
  • The first line is the frequency in Hz.
  • The second line is the musical note and any offset in cents.
  • The following lines are the magnitude, magnitude difference, phase difference, or coherence values, depending on which value grids are enabled.
Hold down option while dragging to see the difference between where the cursor was clicked and the current position

Markers

command-click in the meter to create a marker.
  • Click and drag the marker to reposition.
  • Press esc to dismiss the details.
  • Click on the name or position details to edit
  • Press the button to edit the color or to remove the marker

Controls

Hover the mouse over the meter to reveal the control bar.
Show the meter configuration popover
Show the traces configuration popover
Pause the meter
Run the meter
Reset the meter values

Meter Configuration

Click the name to reveal settings for that section.

General

  1. Rotate the meter 90° counterclockwise
  2. Flip the meter horizontally or vertically
  3. Choose a color for the background
  4. Choose a color for the crosshairs

Rulers

  1. Click to select a ruler to configure
  2. Select to show the ruler
  3. Select the size of the ruler text
  4. Select the direction the text will be written
  5. Choose a color for the ruler text
The values shown on the ruler will depend on the orientation of the meter.

Grid

The checkbox controls the visibility of the grid, and the color picker controls the color
  1. A common logarithmic grid in Hertz
  2. A linear frequency grid in Hertz
  3. A grid for critical frequencies*
  4. A grid that shows the positions of musical notes
  5. A common magnitude grid in dB
  6. A grid for the magnitude difference in dB
  7. A grid for the phase difference in degrees
  8. A grid for the coherence value, a normalized value from 0.0 - 1.0
* Critical frequencies/bands are a pre-defined set of bandwidths that are designed around human hearing response.

Range

  1. Select the domain to configure

Frequency Range

  1. Set the frequency scale as logarithmic (common) or linear
  2. The minimum frequency to be displayed in the meter
  3. The maximum frequency to be displayed in the meter

Magnitude Range

  1. The minimum magnitude to be displayed in the meter
  2. The maximum magnitude to be displayed in the meter

Magnitude Difference Range

  1. The dB above and below the center line to be displayed in the meter

Phase Difference Range

  1. The degrees above and below the center line to be displayed in the meter

Overlay

  1. Select to show the overlay
  2. Select to display the overlay colors as high → mid → low → mid → high
  3. Rotate the overlay 90° counterclockwise
  4. Flip the overlay vertically or horizontally
  5. Select the color set to use
  6. Set the intensity/opacity
  7. Set the position of the transition between the low color and the mid color
  8. Set the position of the transition between the mid color and the high color

Traces

Traces compute and display the analysis results of the audio.
  • All traces can be configured independently or as a group.
  • One or more traces can be visible at the same time - even of different kinds.
  • Trace values can be "frozen" and saved and recalled as snapshots.
  • Trace values can be exported to files in .csv or .frd file formats

Magnitude Trace

  • Given one or more audio inputs, combines them into a single audio signal
  • Using an FFT, converts the audio signal into its frequency components
  • Displays the magnitude (or level) of the frequencies
  • Magnitudes can be grouped together visually to make them easier to view
  • Applies responses to make the values easier to watch over time
Useful For...
Visualizing frequency responses, harmonic series, acoustic resonances, and more.

Magnitude Difference Trace

  • Takes two discrete audio inputs with an optional delay on one input
  • Using an FFT, converts the audio signals into their frequency components
  • Displays the difference in magnitude in dB at each frequency
  • Use rulers or crosshairs to determine which direction references which audio input
  • Magnitudes can be grouped together visually to make them easier to view
  • Averages the results to make the values easier to watch over time
Useful For...
Checking stereo harmonic balances and acoustic resonances.

Phase Difference Trace

  • Takes two discrete audio inputs with an optional delay on one input
  • Using an FFT, converts the audio signals into their phase components
  • Displays the difference in phase in degrees at each frequency
  • Use rulers or crosshairs to determine which direction references which audio input
  • Averages the results to make the values easier to watch over time
Useful For...
Finding phase issues with respect to frequencies between two signals.

Coherence Trace

  • Takes two discrete audio inputs with an optional delay on one input
  • Using an FFT, converts the audio signals
  • Calculates the coherence between the two signals
Useful For...
Determining the "quality" of spectral comparisons.

Traces Configuration

The area on the left lists the traces in the meter.
The area on the right allows configuration of the selected traces. Click the name to reveal settings for that section.

Trace List

  1. The list of traces in display order. Press return to edit the name
  2. Select a trace to add, or duplicate a selected trace
  3. Click to delete the selected traces
  4. Load or save a snapshot of a trace
  5. Export the values of the selected trace to a text file

Source — Combined

This panel appears for traces that combine inputs for analysis
  1. The audio inputs to combine.
  2. The method used to combine the channels.
    • Sum: adds the samples together
    • Difference: even numbered channels are subtracted from odd numbered channels
    • Average: the samples are added together and divided by the number of channels
    • Average Difference: even numbered channels are subtracted from odd numbered channels and the result is divided by the number of channels
  3. Select the response rise and fall times.
  4.   Rise Time Hold Time Fall Time
    Digital 9.5dB in 1.7ms none 20dB in 850ms
    PPM Type I 9.5dB in 1.7ms none 20dB in 1.7s
    PPM Type II 9.5dB in 1.7ms 100ms 24dB in 2.8s
    VU 40dB in 300ms none 40dB in 300ms
    Nordic 14dB in 5ms none 20dB in 1.5s
    BBC/EBU 14dB in 5ms none 24dB in 2.85s
    Peak Hold (Short) immediate 0.7s 60dB in 300ms
    Peak Hold (Long) immediate 2.0s 60dB in 300ms
    Peak Hold (Infinite) immediate forever none
  5. The amount of gain to be added to the combined result.

Source — Dual

This panel appears for traces that compare two distinct inputs for analysis
  1. Select the channel to be used for source X.
  2. Select the channel to be used for source Y.
  3. Set the amount of time difference to add to source Y. Negative values are allowed.
  4. Set the length of the preceding results to include in the displayed results.

Analysis

  1. Select the windowing function to apply to the audio before analysis.
  2. Select the number of samples to gather for analysis.
  3. Select the interval used to group the frequencies into more useful results.
  4. Select the method used to average the results.

Display

  1. Select the stroke style.
    • Lines: a strip of lines connecting consecutive result values.
    • Bars: a strip of lines that outline the magnitude of the frequency groups.
    • Peak Bars: short lines drawn at the magnitude across the frequency group.
    • Peak Follower: a small triangle pointing down to the frequency group with the highest magnitude.
  2. Select the fill to draw between the stroked line and the zero line.
    • None: no fill is drawn.
    • Solid: the color of the trace.
    • Translucent: the color of the trace with half the opacity.
    • Faded: the color gradiated from transparent at the anchor to opaque at the top magnitude.
  3. Select the thickness of the stroked line.
  4. Select the base color.

Control

  1. Select to run the trace. Deselect to pause.
  2. Select to hide the trace.
  3. Set the amount of overlap to use between analysis windows. Faster speeds can result in less accurate results.
  4. Resets any stored magnitudes.